1. Field of the Invention
This invention relates generally to an actuator and more particularly to a rotary hydraulic actuator which is self-powered.
2. Brief Description of the Prior Art
Rotary hydraulic actuators of the vane type having a shaft rotatable in response to rotary movement of the vane have been proposed generally to provide angular positioning of the shaft relative to a fixed reference. Examples of such an actuator are disclosed in Floer U.S. Pat. No. 3,279,329 and Higuchi U.S. Pat. No. 3,750,535.
The constructions disclosed in the above patents are suitable where absolute angular positioning is required. However, these actuators require a complex hydraulic system, including a pump, to control angular position. Furthermore, such constructions are not directly applicable to mechanical systems requiring relative angular positioning between a pair of loads. One such mechanical system is a dual permanent magnet generator (PMG). In a dual PMG the relative angular position of a pair of rotors is controlled to provide for voltage regulation. The rotors may be coaxial, or alternately, may be positioned in a side-by-side relationship.
Frister U.S. Pat. No. 3,713,015 shows a dual PMG wherein controlled axial movement is converted, by a helical gear, to angular motion to provide relative angular positioning between a pair of rotors. Though such a system should work well in theory, in practice, particularly in high speed generators, difficulty in effecting required voltage regulation may be encountered. In particular, loading of the rotor components due to centrifugal force and other operational factors may render it difficult to achieve relatively precise angular adjustment between the rotors. To the extent that precise adjustment is hindered, good control cannot be achieved.
The present invention is intended to overcome these and other problems associated with actuators.